Such optoelectronic apparatuses with light-transmitter, light-conductor and light-receiver are used, for example, for transmitting digital and/or analog signals between galvanically separated circuits.
Galvanic separation of circuits is required especially in various areas of industrial measurements and automation technology, when explosion protection specifications apply. For example, in the case of field devices used for measuring and/or controlling flow, pressure, fill level, temperature and/or the like, galvanic separation is used for achieving explosion protection. Galvanic separation is, in such cases, to be provided both for the field devices commonly referred to as 4-conductor devices, which are supplied with electrical energy, or power, over at least one special grid line, and, as required, for the field devices commonly referred to as 2-conductor devices, in the case of which energy supply and data transmission occur over one and the same line. Examples of field devices having an apparatus formed as an optocoupler for galvanically separating circuits are described in, among others, EP-A 525 920, U.S. Pat. Nos. 6,684,340, 6,624,418, 4,654,771, or WO-A 04/048905.
Apparatuses of the aforementioned kind suitable as optocouplers are described, for example, in EP-A 103 032, U.S. Pat. Nos. 6,947,620, 6,633,030, 6,509,574, 5,614,131, 5,349,504, 4,367,483, 4,307,297, 4,124,860, 4,100,422 or 3,774,021. The optoelectronic apparatuses disclosed therein have, in each case, at least one light-emitting, optoelectronic, first functional element, for example a light-emitting diode, as well as at least one light-sensitive, optoelectronic, second functional element, for example a photodiode. The light emitting functional element is appropriately caused to function during operation by an electrical signal and emits, at least at times, light, while the light-sensitive, functional element is caused to function by light appropriately falling thereon. For transmitting light emitted from the light emitting, functional element to the light-sensitive, functional element, there is additionally provided in the optoelectronic apparatus, in each case, at least one light-conducting, third functional element composed, at least in part, of transmissive material, for example, translucent plastic or glass. During operation, this third functional element conveys light coupled into it. The third functional element has a first boundary surface facing, and in-coupling light from, the first functional element, and a second boundary surface, in turn, out-coupling internally conveyed light. The second boundary surface faces the second functional element. The light-coupling, boundary surfaces of the third functional element of the apparatuses disclosed in EP-A 103 032, U.S. Pat. Nos. 6,947,620, 6,633,030, 6,509,574, 5,614,131, 4,367,483, 4,307,297, 4,124,860, 4,100,422 or 3,774,021 are, in each case, formed essentially planarly. Additionally, such surfaces also have, in each case, a surface normal extending parallel to an imaginary principal ray axis of the, in each case, associated optoelectronic, functional element. In this connection, the imaginary principal ray axis of the first functional element represents a direction of maximum intensity of the light emitted during operation from the first functional element, while an imaginary principal ray axis of the second functional element represents a direction of maximum sensitivity of the second functional element to light incoming during operation. Alternatively to the aforementioned planar, light-coupling boundary-surfaces, it is possible, as proposed, for example, in U.S. Pat. Nos. 6,947,620 or 5,349,504, additionally also to use lens-shaped, light-coupling boundary-surfaces on functional elements of the described kind.
In order that such optoelectronic apparatuses used for signal transmission can satisfy the explosion protection required in industrial measurements and automation technology, also minimum spacings must be maintained between galvanically separated, current conducting components, as well as also minimum values for air distances, insulation thicknesses, and current creep paths. Thus, for instance, in the case of a maximum allowable voltage of 375 V, the air distances and creep path lengths between galvanically separated circuits are 10 mm and the thickness of solid insulation must amount to at least 1 mm. These distances, or separations, relate, in such case, especially to the minimum separations between the connections and conductor traces of the circuits coupled by means of such optoelectronic apparatuses and carrying electrical current during operation. Furthermore, these apparatuses serving as optocouplers must fulfill increased requirements with respect to temperature resistance and explosion endangerment risk, as well as also with respect to possible damage scenarios associated with possibly occurring overloads.
In order, despite the demanding technical aspects of the safety requirements, to enable for such optoelectronic apparatuses a highest possible light-coupling factor, as well as compact as possible physical shape, their functional elements serving as light conductors are usually, as shown for example in U.S. Pat. Nos. 6,947,620, 5,614,131, 4,367,483 or 4,124,860, formed in the manner of optical lenses, at least in regions which are to redirect the transmitted light at least partly by reflection, especially also total reflection.
However, the manufacture of light conductors, which are partially lens-shaped, is relatively complicated. Additionally, the lens form of the light conductor, be it in the regions of the light-reflecting boundary surfaces or in the regions of the above-mentioned, light coupling boundary surfaces, also requires a precise positioning and orienting of each of the functional elements directly participating in the optical transmission, along with an increased adjustment effort during manufacture or during installation. This is especially true also for the case in which, as also proposed, for example, in U.S. Pat. No. 6,947,620, the optoelectronic apparatus is to be created first in the course of populating circuit boards carrying the circuits. As a result of this, in turn, also the manufacture of such an optoelectronic apparatus is, altogether, comparatively expensive.